Why we built a 0% alternative to SumUp (and the refund fee that pushed us over the edge)

If you run a small offline shop in Europe, you probably know SumUp. Flat 1.69% per tap, cheap reader, no contract. Honestly a great product, and a big reason card acceptance reached so many tiny merchants.

But I kept staring at one number while building in this space. A shop doing €50,000 a month at 1.69% hands over €845 in fees. SumUp gives no volume discount, so that rate never improves no matter how big you get. And here's the one most people miss: on a refund, SumUp keeps the original processing fee. You refund a sale and you still eat the cost of having made it. For anything return-heavy, that's a quiet tax.

So I went looking for the "no transaction fees" alternative everyone searches for. The dirty secret: there basically isn't one on cards. Zettle and Square sit at ~1.75%, a rounding error off SumUp. SumUp's own "cheaper" plan still charges ~0.99% plus a monthly fee. Every one of them is a variation of pay the card networks a slice of every sale, because the 1.69% exists for a reason: every swipe routes through Visa/Mastercard interchange and scheme fees. Shop for a thinner slice all you want, on the card rails there's always a slice.

The only way to actually hit 0% is to not take that route. That's the bet behind Zahlo (zahlo.eu): QR-based payments for German offline shops. Customer scans a code, money moves account-to-account, the card-network toll isn't in the path. So we charge 0% transaction fees, no chargebacks, and there's no card reader to buy because no card is being read. Built-in inventory and auto-reconciliation on top.

I won't pretend it's free of trade-offs. Your customer scans instead of taps, so it shines for a Späti or kiosk doing 200 small-ticket sales a day, less so where everyone insists on contactless cards. But for the right counter, 1.69% on a €4 coffee is pure margin loss, and skipping the networks is the whole win.

Genuinely curious where you'd push back. If you sell offline: would your customers scan a QR to pay, or is tapping a card still non-negotiable? And is there a 0% model you've seen work that I'm missing?